1. Field of the Invention
This invention relates generally to window construction, and more specifically, to an improved configuration for moving the sash members of sliding sash windows for effecting superior sealing properties.
2. Cross-Reference to Related Patents
To the extent disclosures in U.S. Pat. No. 3,538,642 issued on Nov. 10, 1970, to Fredricksen are necessary for understanding this invention, they are herein incorporated by reference into this document.
3. Description of the Art
The most popular window configurations having movable sashes are the casement, the double-hung and the sliding or gliding types of windows. Besides their different aesthetic properties, each has unique functional characteristics that must be considered when selecting the proper type of window for the desired application. For example, a casement window which is typically mounted for hinged movement about a vertical axis along one edge of the window is easily opened by means of a simple crank lever and has characteristically offered an excellent weathertight seal between the movable sash and the window frame. However, such windows have the disadvantage of opening outward, thereby being susceptible to damage, requiring extended eave overhang protection, and typically require insect screens to be located on the inside of the window frame, a condition which allows for undesirable collection of insects and debris between the screen and the sash.
Double-hung windows generally include a pair of sash members which move vertically within a weatherstripped frame member. Biasing or counterweight means located within or on the frame of the window are typically used to facilitate operator movement of the sashes. Insect screens and/or additional fixed glazing panels can be mounted on the outside of the window. Due to the slidable property of the window relative to its weatherstripping, the doublehung window does not generally enjoy the same weathertight seal properties of a casement window.
Sliding or gliding windows generally include a pair of sash members one or both of which are horizontally movable within a frame. As with the double-hung type of window, an insect screen or additional glazings can be mounted on the outside portion of the window frame. Generally, only one of the sash members is moved at a time, as directed by guides or tracks formed within or extending from the upper and lower jamb portions of the window frame. Because of the sliding nature of this type of window and the difficulty in providing a tight seal between the two sash members, the sliding window has generally not been as weathertight as its casement counterpart.
It is desirable in a sliding window configuration to maintain a separation spacing between the window sashes when moved relative to one another, so as to minimize frictional wear to and damage of the weatherstripping parts during the sash movement process. Another desirable feature for a sliding window is that the moving sash slide or glide relatively freely with respect to the track or guide, and not require undo pressure or strain to be exerted by an operator to open, close or lock the window into sealed closure. Further, the track or guide and any moving parts associated with moving the window along such track or guide should be highly reliable and relatively maintenance free. It is also desirable to design the sliding window in a manner such that its weathertightness properties equal or approach those of a casement window.
While a number of sliding window configurations are known, none has displayed the unique combination of properties and design attributes which simultaneously satisfy the above design goals for a sliding window. For example, early sliding window configurations employed recessed tracks in the upper and lower window frame members along which the movable sash members moved as directed by guide pins projecting from the top and bottom of the movable sash members. The tracks were obliquely aligned with respect to the window frame so as to enable the movable sash to simultaneously travel longitudinally along the window frame and in a direction away from the other sash member so as to prevent frictional engagement with the second sash member during movement. The recessed groove required excessive cleaning and maintenance, was susceptible to rapid operative degradation and was difficult to seal.
A later development, disclosed in cross-referenced U.S. Pat. No. 3,538,642 eliminated the problems associated with a recessed groove guide by providing an extruded self-cleaning track on the window frame sill for directing movement of the window sash therealong as assisted by stationary glide mechanisms mounted within the bottom portions of the movable sash members. The extruded track was self-cleaning in nature and was segmented into four different sections having varied elevations and angles so as to direct the movable sash into sealing engagement at closure and away from the adjacent sash during sliding movement in the open position. While this invention provided many advantages over earlier sliding window designs, due to the curved and segmented nature of the track, excessive operator pressure could at times be required to properly move the sash member along its intended path. Further, since the extruded guide member was only used along the bottom of the window frame, the closure seal along the upper portion of the window was not as weathertight as desired.
A more recent sliding window design is illustrated by U.S. Pat. No. 4,682,455 which also uses an extruded guide for directing a movable window sash member carried by a roller carriage assembly. The window assembly of this design uses compression seals, but requires an operator to impart the required compression force to the seals by physically pulling the window sash at its closure position in a direction transverse to the longitudinal movement of the window.
Therefore, while each of the prior art sliding window configurations satisfies one or more of the desired design attributes for a sliding window, none has provided a design which collectively satisfies all of the desired design attributes at the same time. It is believed that the present invention does so. The present invention provides a self-cleaning, relatively maintenance-free straight guide track. The movable sash members of the sliding window of this invention are carried by low-friction glide members which require minimal operator effort to move the sash members along the guide or track. The glide members are uniquely configured to cam and hold an entire movable window sash member into compressive sealing engagement at the point of closure, as a logical extension of the longitudinal movement of the window within the frame, and without requiring additional pulling motion by the operator. The weathertightness of the seal provided by the structural design of the window of this invention compares favorably with that provided by a casement type of window.